Posted: 1/5/2014 9:05:19 PM EDT
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For the moment I'm confined to 2m/70cm. I'm using a roll up J pole (N9TAX) but plan to make that part of my to-go kit rather than leave it as a permanent fixture to the house.
I'd like to discuss options before spending any more money on either tools/materials or finished product. Options I'm looking at are an Arrow Antenna J Pole or building a pair of horizontally polarized loop antennae (one for each band, stacked vertically a few feet apart). Are there any other options I should be considering? My understanding (based on one of the test questions) is that the loop style of antenna is a better radiator and receiver. A single loop for VHF/UHF is small enough I could put 4 of them on my roof and no one would even notice. (I currently rent the house and do not know if there's an HOA involved or not.) So, while I'd like to have a general discussion on the subject, I do have some specific questions. Let me get those out of the way first.
ETA Question #4 and related image. |
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What is your intended use of the radio? Repeaters and most local comms use vertically polarized antennas, so you are going to experience massive losses if you try to communicate with a repeater using a horizontally polarized antenna. Typically, horizontal polarization is used for weak signal work (SSB).
If you want a vertically polarized dual band antenna, also consider the Diamond X30/X50 series. |
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I don't know about the loops but within a day or two I should have a Arrow J-Pole delivered.
More specifically the Arrow "OSJ - Model OSJ 146/440 Dual Band J-Pole with Extra Labor Charge for Two Piece Element" and I can take detailed photos if needed. The reason I bought this one was because it can be broken down to more of a compact length ultimately for use in portable operations like camping and Field Day. My home brew copper J-pole is 5'6" tall and only 2 Meter, the Arrow "two piece element" model is much more compact and dual band too. I do plan to add a 2 Meter beam the "Arrow II 146-4BP & Arrow II Mounting Bracket (Three Piece Boom)" same reason for a more compact storage. |
| I have the dual-band Arrow J-Pole and love it. I have it mounted on an old plant stand in the living room until I can get it outside. I easily hit repeaters at 12 to 20 miles in wooded, hilly terrain. It has 1.0 SWR on 70 cm and 1.2 - 1.3 on 2 m using LMR400 to feed it. |
On line-of-sight (LOS) paths, it is important that the polarization of the antennas at both ends of the path use the same polarization. In a circular polarized system, both antennas must have the same polarity. If not, an you may have a loss of 20 dB or more. Most mobile radios that you may want to talk to simplex are vertically polarized, so a 20db difference means not hearing or working that station.
Stealth may be your primary concern, but a horizontally polarized antenna is not the solution you are looking for. You would be better off concealing an antenna in your attic space if possible than using a circular polarized antenna. |
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Here are the pics of my new Arrow dual band "two Piece" J-pole. I am impressed in the quality. It looks like the aluminum base and mount are anodized in silver. The shafts appear to be in-the-white.
I have access to a full machine shop and my cost for materials and shop setup time for all operations to create this would have at least cost 3 times the amount (if I had to pay for it). I wouldn't hesitate to buy a second one. I was mostly impressed with the extra threaded hole for a storage location when breaking down the long pole. Next to my 2 Meter only copper J-pole with Camo paint job. 
With the long pole stored on the angle base. The poles are straight my camera bends the image a little. 
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| I have a Comet GP-3 2M/440MHz antenna mounted on a Radio Shack TV antenna mast strapped to my chimney. It's been up there for over 8 years with no problems and for an omnidirectional antenna, really reaches out. |